Plumbing and water heaters
How heat pump hot water heaters work and why you should get one
...heat source in a home is an air source heat pump, as the water heater can in effect 'borrow' the efficiency of that heat pump, which on average is about 3 times more efficient than most other heat sources. See here for an article on how heat pumps work.
To be able to easily compare the performance of different heat pum...